Ubiquitin-Dependent Sorting in Endosomes and the TGN

描述(申请人提供)：将蛋白质送到溶酶体进行降解是细胞用来控制细胞表面蛋白质活性的主要机制之一。膜蛋白的泛素化是其向溶酶体分选的主要信号。翻译后泛素(Ub)与靶蛋白的连接启动了它们从细胞表面的内化和转运到多囊内体/多囊泡(MVB)的腔小泡。已知一系列ESCRT(运输所需的内体分选复合体：ESCRT-0、I、II、III)协调泛素化的膜蛋白货物(Ub-Cargo)的分选和MVB腔小泡的形成，从而在溶酶体降解过程中发挥关键作用。然而，ESCRT蛋白是如何识别和移动Ub-Cargo的，以及它们可能如何参与协调Ub连接酶和Ub肽酶的活性以修饰和调节Ub-Cargo的命运，目前还不清楚。这里提出的工作有两个主要目标：第一个是确定哪些蛋白质作为内体Ub分选受体，以及它们如何与其他功能协调地移动Ub-Cargo。第二个目标集中在一个新兴的概念上，即由于泛素化是动态的，因此存在许多情况下，Ub连接酶和肽酶可以竞争最终的货物处置。我们现在提出，作为“ESCRT-0类”蛋白平行工作的其他蛋白质复合体，以及其他内体分选复合体，与Dub和连接酶结合，显著影响特定Ub-Cargo的分选命运。具体目的是：研究ESCRT-I和-II对Ub结合的作用。测试交替的“ESCRT-0-样”复合体的功能。检测脱氢酶在回收内体蛋白质中的作用 公共卫生相关性：未能将特定的膜蛋白靶向溶酶体会导致通道、转运体或信号受体不适当的过度活跃，进而导致许多疾病，包括癌症、代谢紊乱、发育异常、心脏病和高血压。这里提出的工作将研究生化和细胞生物学过程，以确保正确识别和分类溶酶体中以泛素标记的膜蛋白。我们相信，这样的理解将为操纵溶酶体降解过程的治疗干预开辟新的途径，以针对一系列生物过程。

DESCRIPTION (provided by applicant): Sending proteins to the lysosome for degradation is one of the chief mechanisms cells use to control the activity of cell-surface proteins. Ubiquitination of membrane proteins serves as a major signal for their sorting to lysosomes. The post-translational ligation of ubiquitin (Ub) to target proteins initiates their internalization from the cell surface and their transport into lumenal vesicles of multivesicular endosomes/multivesicular bodies (MVBs). A series of ESCRTs (Endosomal Sorting Complex Required for Transport: e.g. ESCRT-0,I,II,III)) are known to coordinate the sorting of ubiquitinated membrane protein cargo (Ub-cargo) with the formation of MVB lumenal vesicles and thus play critical roles in the process of lysosomal degradation. Yet, how ESCRT proteins recognize and move Ub-cargo as well as how they might participate in coordinating the activity of Ub ligases and Ub peptidases to modify and thus regulate the fate of Ub-cargo are unclear. The work proposed here has two main objectives: The first is to establish which proteins serve as endosomal Ub sorting receptors, and how they move Ub-cargo in coordination with their other functions. The second objective centers on the emerging concept that since ubiquitination is dynamic, there are many instances in which Ub ligases and peptidases can compete for the final disposition of cargo. We now propose that other protein complexes that work in parallel as "ESCRT-0- like" proteins, as well as other endosomal sorting complexes, associate with DUbs and ligases to acutely influence the sorting fate of specific Ub-cargo. The Specific Aims are to: Investigate the roles of Ub-binding by ESCRT-I and -II. Test the function of alternate "ESCRT-0-like" complexes. Test the role of Deubqiutinating enzymes in recycling proteins from endosomes PUBLIC HEALTH RELEVANCE: Failure to target particular membrane proteins to lysosomes leads to inappropriately hyperactive channels, transporters, or signaling receptors, which in turn contribute to a number of diseases including cancer, metabolic disorders, developmental abnormalities, heart disease, and hypertension. The work proposed here will investigate the biochemical and cell biological processes that ensure proper recognition and sorting of membrane proteins that are marked by ubiquitin for degradation in lysosomes. We believe that such understanding will open new avenues for therapeutic interventions that manipulate the process of lysosomal degradation to target a range of biological processes.